### Theory:

Anything that is not straight is referred to as a curve.
There are different types of curves. Some of which are:
• Simple curve
• Non-simple curve
• Open curve
• Closed curve

A curve that does not cross itself is called a simple curve.

A curve that crosses its own path is called a non-simple curve.

An open curve is a curve whose endpoints do not meet at any point. It has two endpoints.

A closed curve is a curve, which has no endpoints and enclosed an area.

A closed curve contains $$3$$ parts. They are:
• Interior of the curve
• Exterior of the curve
• Boundary of the curve

1. Interior of the curve:

The inside / inner region of the curve is referred to as the interior of the curve. In the above figure, point $$A$$ lies on the interior of the curve.

2. Exterior of the curve:

The outside / outer region of the curve referred to as the exterior of the curve. In the above figure, point $$B$$ lies on the exterior of the curve.

3Boundary of the curve:

The curve, which divides the interior and exterior part, is called a boundary of the curve. In the above figure, point $$C$$ lies on the boundary of the curve.

Important!
The interior and boundary of the curve together are called "the region" of the curves.